Last flag flying is not the best or worst Richard Linklater movie. Have you even seen Boyhood? Why waste 10 years of your life when you can use CGI to make someone look younger? Anthony Hopkins judges you. Jokes apart, Boyhood is a really good movie but ( don't kill me for saying this), I would prefer School of rock to this. Imo nothing can beat the 'Befores'. That's a conversation for another day. So saying LFF is not his best/worst is not saying much because he has seen both ends of the spectrum (Don't get me started on EWS).
I went into this thinking this is gonna be caffeine for the Oscar voters. An argument can be made that it is. But, who doesn't love a lightweight buddy road-trip movie? Does it have memorable moments? Maybe yes/ maybe no. But while watching, I really don't care what's gonna stay with me for the next 1 year. I know those are pretty low expectations from someone who had me memorize the whole before sunrise. But, I appreciate the honesty in which the scenes are shaped. So I understand when in movies like this craft takes a backseat.
If I have to be harsh then yes, the characters are caricatures and disappoint you if you hope that would grow. There are cheesy moments scattered throughout the movie (One involving the vets trying to buy a mobile phone in the early 2000s) and only end up leaving the tiniest smiles.
Credit where it's due, RL handles the emotional scenes very well and this is where you appreciate his brilliance.[spoiler]My favourite being Carell wanting to see his son.[/spoiler] This scene could've gone wrong in more ways than one. But Linklater takes care of it and this is where his masterful storytelling and direction mix perfectly. The cast is obviously a strong point. I'm mostly amazed by Carell who is now second to only Jake Gyllenhaal when it comes to choosing different and novel characters (And that's a big compliment).
So, to end with I would say that this movie doesn't upgrade slash downgrade my appreciation for Linklater but I'm really glad I didn't miss it. Which is what the whole point of making a movie should be, no?